$ sudo apt-get update
$ sudo apt-get install linux-patch-xenomai 

linux-patch-xenomai is installed in your system.

Make ensure the linux-patch-xenomai package were installed using the commands given below,

$ sudo dpkg-query -l | grep linux-patch-xenomai *

You will get with linux-patch-xenomai package name, version, architecture and description in a table

linux-patch-xenomai package basic information: